The present invention relates to belt sanders and relates more particularly to an improved sanding mechanism for a belt sander which can effectively sand a workpiece through two different angular directions and eliminate grinding burn problems.
In wood-working, belt sanders have been commonly used for sanding the surface of a wooden board so as to make it smooth. In regular belt sanders, the sanding mechanism, as shown in FIG. 1, is generally comprised of two sanding heads, namely, a front sanding head for primary sanding and a rear sanding head for fine finish sanding. In this sanding mechanism, the sanding direction of the front and rear sanding heads is parallel with the feeding direction of the workpiece to be polished. Because the sanding belt of the front sanding head and the sanding belt of the rear sanding head are rotated in the same direction, a fine finish is difficult to achieve and grinding burn problems tend to happen. Further, because there is only one set of sanding heads (the front and rear sanding heads) installed above the conveyer, a workpiece shall be processed twice so that the two opposite sides thereof can be completely polished. Therefore, this sanding mechanism is not efficient in use.
The present invention has been accomplished to eliminate the aforesaid disadvantages and problems. It is therefore an object of the present invention to provide a sanding mechanism for a belt sander which is easy to operate and can eliminate grinding burn problems. It is still another object of the present invention to provide a sanding mechanism for a belt sander which can simultaneously sand the two opposite surfaces of a workpiece at the same time. According to the present invention, two sets of sanding heads are provided for sanding the upper and bottom surfaces of a workpiece at the same time. Each set of sanding heads includes a front sanding head disposed at a 30.degree. to 60.degree. angle relative to workpiece feeding direction for primary sanding operation and a rear sanding head disposed in parallel with the workpiece feeding direction for fine finish sanding operation. Guide wheels are fastened in the front sanding head for guiding a workpiece in the workpiece feeding direction for positive sanding operation.